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by esprehn 1100 days ago
Go slices are passed by value so there's no way for clear() to resize the underlying array without reassignment.

I suppose it could have been x = clear(x) or clear(&x), but certainly if you understand Go semantics then seeing any function call do Foo(slice) already signals that the call can't modify the length since there's no return value.
2 comments
nu11ptr 1100 days ago
This is a great example of why I dislike Go. It is not obvious that a slice is passed by value while a map is not or why. Therefore every action on it feels a bit weird because of that, and now you have functions like "clear" that take a very non-obvious action. Personally, I'd rather have pass-by-value return an error and only allow pass-by-reference (better: they should have had maps and slices be pointers). I'm not sure I'd ever use a function that set every value to its zero type.
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esprehn 1099 days ago
I agree the semantics seem weird, I've occasionally wanted the equivalent of x = clear(x) but I can't think of a time when I've wanted to set all the values to the zero value.

The bug doesn't seem to discuss use cases for it either. The most I could find is: https://github.com/golang/go/issues/56351#issuecomment-13326...

Which boils down to "doing what clear(slice) does cannot be implemented efficiently today" but I'm not sure how having an efficient way to do something folks don't want is useful?

There's already a memory clearing optimization in the compiler: https://github.com/golang/go/issues/19266

So yeah I'm not sure under what situations folks will use clear(slice).

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aatd86 1099 days ago
You often do it in Go to avoid pointing at something needlessly which would delay or even keep that something from being garbage collected.
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binwiederhier 1099 days ago
That's actually a great explanation of why it's not easy to implement the clear function the way it makes sense for slices. However, this is a built-in, not a normal function, so they could make it do whatever they like, including doing the intuitive and desired thing, no? It seems to me that they've just created another "loop variable gotcha" type situation...
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